OLED Watch V2

The second version of the OLED watch PCBs turned up yesterday, so this morning I assembled a board and programmed the firmware. The boards are in a nice blue colour this time:

The assembled board is quite neat:

The firmware ran first time, as I had altered the breadboard version to match the layout and adjusted the firmware. Let's see how well it works...

Watch Prototype Failure

Drat! My watch prototype now only ever looks like this:

There's no response to anything and attaching the battery just causes it's voltage to drop to about a volt, which isn't good. I noticed that the battery voltage had started to drop quite quickly a few days ago, but after coming back from a weekend away I found it was completely dead, the battery at a low voltage and no way to resurrect it.

I'm not too surprised, as I was using rechargeable 2032 batteries and they run at 3.6V not 3V, and the PIC16LF707 has a maximum operating voltage of 3.6V. All would be OK, except that the actual voltage of a charged battery is about 4V, so i have been over-volting the part. So in a way there's good news as I know what the problem is. For the PCBs i have some PIC16F707 parts which I will use, they have a maximum operating voltage of 5V so should be OK. I think the power for that part may be a bit higher, but as I'm probably planning to use rechargeable batteries now that shouldn't be a problem. With the display active all hopes of a long battery life go out of the window anyway...

More Watch

The display is now working, I have functions that display integers and strings and an X-Y positioning function. The display shows text:

The capacitive touch sensors are working too, That's what the OFF OFF means, two sensors are currently off (because I have no finger near the wires). This video shows the capacitive sense inputs in action. You can see OFF swap to ON when I get near the sense wires.

Unfortunately I think the processing of the sense inputs may take up too much current and shorten battery life. I may have to go for the less cool mechanical switches.

Watch

The watch firmware now has a basic digital display and a crude analog display.

The display also has a display of battery voltage. The idle loop is now driven by timer 1 in the PIC, which runs from a 32kHz crystal. It keeps pretty good time and also, with a 2s wakeup time should give a reasonable battery life.

The PCB layout was originally going to be a single sided board, but I found it wasn't really practical, and also had problems printing it on my printer so I've decided to do a double sided PCB and have it made elsewhere on the planet.

The layout was pretty simple, we'll see how good it was when the boards come back.

Watch

I have to send my watch off every four or five years and am then left with no watch for a while. In the spirit of other making, I've decided to have a go at a watch of my own.

This is a breadboarded circuit using the 40 pin DIP chip. I bought a few of the DIP versions as they are much better for prototyping, I don't want to have to build a PCB at this stage.

The OLED display is here, I have written some simple I2C functions to talk to it and  have just sent an initialisation sequence. It's quite a complicated driver and so requires a lot of initialisation just to get to this point. The display pattern is just random RAM data, with some other data written on top.